The prodromal phase of schizophrenia is considered to begin with early subtle changes in behavior and continue until the onset of psychosis. The proposed study is designed to prospectively characterize the prodromal phase of schizophrenia and determine the accuracy with which prodromal symptoms predict schizophrenia. This information, which is not currently available, is essential for establishing effective intervention programs. From a research perspective, since not all individuals displaying putative prodromal symptoms will actually develop schizophrenia, such subjects constitute a new type of population at risk for schizophrenia, referred to here as clinical high risk (CHR). One hundred and twenty CHR patients, 60 normal controls and 60 psychiatric controls diagnosed with attention deficit hyperactivity disorder (included to evaluate specificity), will participate in the proposed five year study. All subjects will be between the ages of 14-21 years. High risk patients will be divided into two groups of 60 patients each: the CHR group, that will consist of patients characterized by social deficits, increasing school difficulties, and odd behaviors; and the CHR+P group, consisting of CHR patients who have also begun to display a range of attenuated positive symptoms. All high-risk patients will be recruited from the Recognition and Prevention of Psychological Problems (RAPP) Clinic. It has been operational for approximately a year and a half under the direction of the investigator and provides treatment to adolescents and young adults considered to be in the prodromal phases of schizophrenia. All study participants will be assessed at base and during regular follow ups, on clinical and neurocognitive characteristics thought most likely to define the prodrome, according to the literature and the pilot work already completed in the RAPP clinic. A number of clinicians and researchers have recently proposed that if treatment were to begin during the prodrome, progression to psychosis might be prevented or, at minimum, delayed and severity reduced. However, the prodrome is currently a retrospective concept that has not as yet been prospectively validated. The overall goal of this project is to assess and prospectively follow adolescents in all four subject groups to establish the sensitivity, specificity and predictive validity of the selected prodromal characteristics. This is expected to provide an evidential base that will lead to a variety of phase-specific interventions throughout the prodrome.